Technical Field
The present invention generally relates to a data access method and a memory control circuit unit and a memory storage device using the data access method.
Description of Related Art
The markets of digital cameras, cellular phones, and MP3 players have expanded rapidly in recent years, resulting in escalated demand for storage media by consumers. The characteristics of data non-volatility, low power consumption, compact size, non-mechanical structure, and fast read/write speed make a rewritable non-volatile memory ideal to be built into portable electronic devices such as notebook computers. Solid-state drive (SSD) is a type of memory storage device using flash as storage media. As a result, flash memory has recently become an important part of the electronic industries.
A memory storage device using the rewritable non-volatile memory as a storage medium is usually disposed with a buffer memory, which is configured to temporarily store program codes or data, or serve as a temporary storage area for data used when background tasks are executed by the memory storage device, and the temporarily stored program codes are stored in buffer units of the buffer memory. For instance, when executing a write operation upon receiving a write command, the controller of the memory storage device writes the data corresponding to the write command into the buffer units and updates a logical unit-buffer unit mapping table, so as to record logical units corresponding to each buffer unit. When receiving a read commend and executing a read operation, the controller of the memory storage device searches for the buffer units storing the data corresponding to the read command according to the logical unit-buffer unit mapping table, and reads the data of the buffer units found.
However, when the buffer memory is already stored with a large amount of data, it takes the controller of the memory storage device a lot of time to search the logical unit-buffer unit mapping table. As a result, the read time by the host system is too long, read speed drops, and the overall function of the memory storage device drops. Accordingly, how to improve efficiency of data reading to increase the overall function of memory storage devices is one of the major subjects for person skilled in the art.
Nothing herein should be construed as an admission of knowledge in the prior art of any portion of the present invention. Furthermore, citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention, or that any reference forms a part of the common general knowledge in the art.